The field of the invention generally relates to end effectors for picking and placing objects, and are typically used with robotic arms for picking up items off a conveyor belt and placing them in bulk packaging.
End effectors, also known as end-of-arm tools, in general are well-known in the art. In the packaging industry, an end effector is typically attached to the end of a robotic arm from a robot such as a Delta Robot. The robot controls the robot arm, which in turn controls movement of the end effector. The robot further includes a rotatable shaft to actuate an actuation mechanism of the end effector, to control movement of individual carrier assemblies. This is done typically to retrieve (pick) items (e.g., candy bars or other food items) from a first conveyor belt, and deliver (place) them into containers such as boxes on a second conveyor belt for retail distribution.
A typical end effector has carrier assemblies that each include a carrier block either fixed to the frame of the end effector, or slidingly engaged to the frame, with one or more pick-up members (typically suction cups) attached thereto and operatively connected to a vacuum source. The quantity and arrangement of the pick-up members may vary depending on the application. For example, an end effector designed to pick up two rows of 8 items each at a first diverged pitch, then place them into packaging in groups of 4 at a second pitch, is referred to herein as a 4×4, 4 by 4, or 4-4, since each side of the end effector would converge the items into 2 groups of 4 in preparation for placing them into the packaging, resulting in groups on each side of 4 and 4.
A first set of parameters associated with the items on the first conveyor belt are determined, such as their shape, dimensions, configuration, orientation, distance between each item, and distance between each group of items, and the first conveyor belt moves at a known speed. These parameters may be preset, programmed, and/or adjusted as needed. Likewise, the packages that receive the items are on a second conveyor belt, with a known second set of parameters that may differ from the first set of parameters. The end effectors are typically custom-designed to accommodate the parameters for a specific application. In this manner, the robot and end effector may be programmed and designed to pick up items at a first pitch and place them into packaging at a second pitch as required.
In order for the pick-up members to pick up items at a first pitch, and place them into a package at a second pitch, the pick-up members must be moveable. Various end effector designs are known for doing so. For example, some earlier successful designs, such as those manufactured by Demaurex, connect (via a connector) to the robot arm, and also have a spindle operatively connected to a rotatable shaft of the robot. The end of the shaft attached to the end effector is attached to a rotary rack and pinion actuation mechanism associated with the end effector, with arms extending out from the pinion attached to carrier blocks on either side of the end effector. As the robot rotates the shaft, the pinion thus rotates, causing the arms to move accordingly, which in turn causes the carrier blocks with the pick-up members to move longitudinally along the body of the end effector. FIGS. 12-13 are selected pages of a Demaurex manual from the year 2000, illustrating several views of the Demaurex end effector with the connector, rack, and pinion annotated. In the Demaurex device, the pick-up members are all directly connected to the arms, and thus move in synch with the arms.
Another known design uses a rotary cam and cam blocks instead of a rack and pinion. See, e.g., U.S. Pat. No. 7,390,040 (Subotincic), the contents of which are incorporated herein by reference. Subotincic describes having only certain pick up members directly connected to the actuation mechanism. Other pick up members are indirectly connected to the actuation mechanism, and are moved by the directly-connected pick-up members by way of tie links. The tie links are small plastic pieces often dangling (not fixed) from the bottom of the end effector and move at high speeds. Also, access to the rotary mechanism is difficult in the Subotincic design, making installation, repair, and maintenance challenging at times.